Mass transfer between two immiscible liquids is the basis for the chemical engineering unit operation of extraction. It is also fundamental in understanding chemical reactions involving two distinct liquid phases. Due to the importance of this process, a variety of methods have been developed to study liquid-liquid mass transfer under laboratory conditions. Lewis cell contactors (essentially a horizontal liquid-liquid interface with rotating distributor rings on both sides of the interface) have been extensively used to study turbulent mass transfer. Applications to systems involving significant diffusional resistance to interphase mass transfer or involving interfacial reaction is limited by the complexity of the hydrodynamics and the accumulation of surface active impurities during reaction. Dispersed phase studies in which the two phases are mixed together are not suitable for fundamental investigations due to the inability to accurately determine the interfacial area and the mixing frequency of the dispersed phase. Use of a drop of one fluid moving or growing in the second fluid has met with some success but the technique has significant limitations because of end effects, excessive contact time, and the coupling of the hydrodynamics to the interfacial properties.
The liquid jet technique has been used extensively to study the interphase transfer of gases and liquids. Although variations have been used the usual method involves passing a jet through a stationary volume of gas or liquid and analyzing samples of the jet fluid (fluid 1). The liquid jet technique is an attractive means of contacting two liquids since it (1) has a constant and measurable area for mass transfer; (2) the hydrodynamics can be approximated to yield good results; (3) the presence of any substantial amounts of surface active impurities can be detected visually through their effect on jet diameter; and (4) the contact time is short allowing enhanced sensitivity to resistances caused by interfacial processes such as interfacial reactions.